Vein 1 and Vein 2have detected through the exploration performed by Metal Mining Agency of Japan.
More than 50 veins and numerous veinlets occur in the Toyoha mining area. The veins have been formed in two stages. The earlier veins are distributed in the northern half of the mining area, and represented by Tajima and Harima veins. The later veins are mainly in the southern half of the area, and represented by Shinano, Izumo, Sorachi and Soya veins. It is obvious that the earlier veins are cut by the later veins, and have been affected by the later mineralization.
The mining area is roughly divided into three mineralization zones by zone boundaries. The polymetallic zone includes xenothermal ores consist of lead, zinc, copper, and minor amount of various metals such as silver, arsenic, antimony, tin, indium, tungsten, cobalt nickel, bismuth, galium, molybdenum etc. Au, Sn, W, In, Bi, Mo, Co, Ni and Ga. manganese is scarce in this zone.
The base-metal zone contains ordinary epithermal ores, including lead, zinc, manganese, copper and minor amount of silver, antimony and arsenic. Little amounts of tin or indium minerals exists only in the later veins or veinlets, which cut through the earlier veins.
The manganese zone fringes these two zones, and the ore consist mainly of manganese carbonates and silicates.